Multiple genotypes of mitochondrial DNA within a horse population from a small region in Yunnan province of China

mtDNA genotypes of six domestic horses (three adult short horses whose heights are under 1 m and three common domestic horses) from a small region of 15 km² in Malipo county of Yunnan province of China were investigated by the technique of restriction fragment length polymorphism (RFLP) with 16 restriction endonucleases which recognize 6-bp sequences. An average of 56 fragments for an individual was obtained. Unlike other domestic animals, this population of horses exhibits high mtDNA genetic diversity. Each of the six horses has a specific mtDNA genotype showing a pattern of multiple maternal origins, as suggested by fossil and literature records. We think the population of horses is an amazing seed-resource pool of horses and hence deserves to be paid more attention from the view of conservation genetics. However, it is also remarkable that we did not find any typical mtDNA genetic markers which would discriminate between short horses and common domestic horses.     

Effect of pH on isoamylase production by Pseudomonas amyloderamosa WU 5315

The isoamylase activity of Pseudomonas amyloderamosa WU 5315 was stable over the pH range from 5.5 to 6.25 while only about 30% of the activity remained at pH 6.5. Low isoamylase activity (418 U ml^-1) was produced by the cells grown at high pH. Activity reached almost 3000 U ml^-1 when pH was kept below 6.0 during the fermentation. With 1% glucose plus 2% maltose instead of 3% maltose as carbon source, however, no pH control was required and the isoamylase activity of Ps. amyloderamosa WU 5315 increased to 3400 U ml^-1.     

离体条件下诱导番茄果实状结构的再生

以番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．）雌蕊和幼果的组织作外植体可以诱导果实状结构的再生。这种果实状结构在离体条件下能培养成熟,成熟时具红色。解剖观察表明：果实状结构由果肉和包围在外面的果皮组成,无种子和胎座。外源激素和外植体年龄的试验揭示：１．以雌蕊组织作外植体时,仅附加外源细胞分裂素就可以诱导果实状结构的再生,外源生长素似乎不是必需的,最高的诱导频率（５０．０％ ）出现在仅附加玉米素０．５ ｍ ｇ／Ｌ的组合。２．从直径４—１２ ｍ ｍ 的幼果上分离的外植体在附加外源激素的培养基上均可诱导果实状结构的再生,但只有从直径８ ｍ ｍ 的果实分离的组织块作外植体并将它们培养在６－ＢＡＰ ２ ｍ ｇ／Ｌ,ＮＡＡ０．１ ｍ ｇ／Ｌ的培养基上时,果实状结构的诱导频率最高（６２．５％ ）。为了探讨在果实状结构再生中表现出来的细胞全能性的表达,提出了植物细胞全能性的部分表达（Ｐａｒｔｉａｌｅｘｐｒｅｓｓｉｏｎ ｏｆｐｌａｎｔ ｃｅｌｌｔｏｔｉｐｏｔｅｎｃｙ）的概念并进行了讨论。     

Selection of antibiotic-resistant mutants with enhanced isoamylase activity in Pseudomonas amyloderamosa

Summary Isoamylase-hyperproducing strains of Pseudomonas amyloderamosa were bred by mutagenesis with UV light and N-methyl-N-nitro-N-nitrosoguanidine (NTG). The selection criterion for such strains was based on the formation of large turbid zones around the bacterial colonies in agar medium containing antibiotics and 1% waxy corn starch. Mutant WN6410 was obtained by treating P. amyloderamosa JD210 with five cycles of 1 × 10⁴ J UV light and one cycle of NTG. P. amyloderamosa WN6410 had 22-fold increase in isoamylase activity when compared to wild-type strain SB15 and the maximal enzyme activity, 5,100 U/ml, could be achieved within 48 h in 2.5 L fed-batch fermentation.     

Neuronal responses to purinoceptor agonists in the leech central nervous system

Exracellular nucleotides like ATP and its derivatives are possible chemical messengers in vertebrate nervous systems. In invertebrate nervous systems, however, little is known about their role in neurotransmission. We have studied the reponse of identified neurones of the leech Hirudo medicinalis to the purinoceptor agonist ATP, ADP, AMP, and adenosine using conventional intracellular microelectrodes and whole-cell patch-clamp recording. Bath application of the agoinsts depolarized the different neurons, but not neuropil glial cells. The most effective responses (up to 10 mV) were observed with ATP (100 μM) or ADP (100 μM) in the noxious and touch cells. In most neurons the nonhydrolyzable ATP derivative ATP-γ-S (5 μM) induced larger depolarizations that 100 μM ATP, indicating that most of the potency of ATP is lost presumably due to its degradation by ectonucleotidases. In medial noxios cells, ATP (100 μM) induced an inward current of 1.7 ± 1.1 nA at a holding potential of ?60 mV. The ATP-induced current-voltage relationship showed an inward rectification and a reversal potential close to 0 m V. In a Na⁺-free extracellular solution, the ATP-induced inward current decreased and in a Na⁺- and Ca²⁺-free saline only a small residual current persisted. The possible P₂ purinoceptor antagonist suramin did not antagonize the ATP-induced current, but itself evoked an inward current and a conductance increase. We conclude that ATP activates nonselective cation channels in medial noxious cells of the leech with the order of potency of purinoceptor agonists ATP ≥ ADP > AMP. The results suggest that these cells express purinoceptors of the P₂ type. 1994 John Wiley & Sons, Inc.     

不同钾水平对钾饥饿墨兰碳水化合物和蛋白质含量的影响

墨兰（Ｃｙｍｂｉｄｉｕｍｓｉｎｅｎｓｅ（Ａｎｄｒ．）Ｗｉｌｌｄ）植株经过钾饥饿后,无上栽培于不同钾浓度的培养液中．随着钾浓度的升高（５ｍｍｏｌ／Ｌ）,体内可溶性糖、淀粉、纤维素和蛋白质含量比对照分别增加１２５、１１７、１２７和４１％,而还原糖和游离氨基酸含量则比对照分别下降４４％和２４％．假球茎是贮藏还原糖、可溶性糖、淀粉、游离氨基酸和蛋白质的主要器官,叶片是纤维素最多的器官．钾供应充足时,叶片丙酮酸激酶活性明显加强（比对照强１５倍）,而硝酸还原酶活性也加强（比对照强０．８倍）．本文对钾促进墨兰生长发育和抗病等原因加以讨论．并初步提出诊断墨兰体内钾状况的三种生理指标．